Systems and methods for monitoring eye health

ABSTRACT

Systems and methods for monitoring eye health. The systems and methods monitor eye health by measuring scleral strain by way of an implantable monitor, a wearable monitor configured in eyeglasses, or an external monitor using a portable tablet computing device. 
     Certain embodiments of the strain monitor may be utilized to measure the strain on any surface to which it is attached, including, but not limited to, the skin of a patient or the surface of a structure such as a building or a bridge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/039,847, filed on Aug. 20, 2014, the teachings of which are expresslyincorporated by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

FIELD OF THE INVENTION

This application relates generally to strain monitoring devices. Moreparticularly, this application relates to implantable strain monitoringdevices for measuring scleral strain, wearable imaging devices formeasuring scleral strain, external tablet-based imaging devices formeasuring scleral strain, and strain monitoring devices for measuringthe strain of a surface to which they are attached.

BACKGROUND OF THE DISCLOSURE

Glaucoma is an ocular disorder characterized by excessive intraocularpressure (IOP), which causes damage to the optic nerve and can lead topermanent loss of vision. It is estimated that over 2.2 millionAmericans have glaucoma but only half of those are aware of it. Glaucomais the second leading cause of blindness in the world. Current methodsfor monitoring patients at risk for glaucoma involve intermittentmeasurements of IOP on an in-patient basis, based on applied pressureand deformation of the eyeball. There also exist devices which attemptto continuously monitor IOP, for example using a pressure sensor whichis implanted in the aqueous chamber of the eye to directly measure IOP.Other methods utilize a strain gauge embedded in a contact lens toindirectly measure IOP. These prior methods are inconvenient, expensiveand measure IOP via a pressure sensor on the surface based on the slightmotion of a foreign, rigid surface that does not record unrestrictedmotion of the cornea or sclera.

It has been found that scleral strain correlates to, and providesadditional information to, IOP. As such, it is desired to have systemsand methods for measuring IOP and/or scleral strain in a non-invasivefashion.

SUMMARY OF THE INVENTION

In one embodiment, disclosed herein are systems for monitoring eyehealth, the systems comprising: a scleral strain monitor adapted to beimplanted in an eye, the scleral strain monitor comprising a sensorconfigured to measure electrical resistance between two electricalconductors, and to generate a signal representing said electricalresistance, and a transmitter configured to transmit the signal; and areader adapted to be located outside the eye, the reader beingconfigured to receive information transmitted by the transmitter.

In another embodiment, disclosed herein are systems for monitoringstructural fatigue in constructions such as buildings or bridges thatcan undergo minute levels of strain. These systems comprise a sensorconfigured to measure electrical resistance between two electricalconductors and to generate a signal representing said electricalresistance, a transmitter configured to transmit the signal, and areader configured to receive information transmitted by the transmitter.

In yet another embodiment, disclosed herein are systems for monitoringeye health, that comprise: a scleral strain monitor comprising a) awearable pair of eyeglasses comprising i) one or more image sensors, ii)a CPU, iii) a memory storage device, iv) one or more connecting wires,and v) and a power source; and b) at least one preselected target regionon or in the sclera, wherein the CPU receives images from the imagesensors and then transmits the images to the memory storage device. Alsodisclosed are methods of using the disclosed systems to determine thehealth of an eye of an individual.

In a further embodiment, disclosed herein are systems for monitoring eyehealth comprising a portable tablet device having a camera, a lensassembly connectable to the camera of the portable tablet, and a comfortpad attached to the portable tablet for maintaining a distance from thetablet and a patient utilizing the system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front view of an implant including a sensor according to anembodiment.

FIG. 1B is a top view of the sensor shown in FIG. 1A.

FIG. 1C is an enlarged view of the sensor shown in FIG. 1B.

FIG. 2A is schematic drawing of an example of a resistor configured foruse in an embodiment.

FIG. 2B is schematic drawing of another example of a resistor configuredfor use in an embodiment.

FIG. 2C is schematic drawing of another example of a resistor configuredfor use in an embodiment.

FIG. 2D is schematic drawing of another example of a resistor configuredfor use in an embodiment.

FIG. 3A is a schematic drawing showing a top view of an example of asensor configured in accordance with another embodiment.

FIG. 3B is a schematic drawing showing another view of the sensor shownin FIG. 3A.

FIG. 3C is a schematic drawing showing a top view of an example of asensor configured in accordance with a further embodiment.

FIG. 3D is a schematic drawing showing a top view of an example of asensor configured in accordance with yet a further embodiment.

FIG. 4 is a schematic drawing showing an example of a system formonitoring eye health, configured in accordance with an embodiment.

FIG. 5 is a front view of an implant including a sensor according toanother embodiment.

FIG. 6 is a schematic drawing of an apparatus for intraoperativelycontrolling eye pressure, suitable for use with an embodiment.

FIG. 7A is a schematic of an example of a resistor from the back sideconfigured for use in an embodiment.

FIG. 7B is a schematic of an example of a resistor configured for use inan embodiment.

FIG. 8A is a side view of an example of a first fixed member of thesensor.

FIG. 8B is a side view of an example of a movable member of the sensor.

FIG. 9A is a view of an example of a scleral strain monitor comprising awearable pair of eyeglasses configured with image sensors, a CPU, amemory storage device, connecting wires, and a power source, wherein theimage sensors are located on the outside frame of the eyeglasses.

FIG. 9B is a view of an example of a scleral strain monitor comprising awearable pair of eyeglasses configured with image sensors, a CPU, amemory storage device, connecting wires, and a power source, wherein theimage sensors are located on the inside nose portion of the eyeglasses.

FIG. 10 is a view of a measurement between two symmetric objects.

FIG. 11 is a view of a measurement between two asymmetric objects.

FIG. 12 is a view of a measurement between two target regions.

FIG. 13 is a view of a measurement of spatial frequency characteristics.

FIG. 14 is a view of a marking tool.

FIG. 15 is a top view of an example of a scleral strain monitor systemcomprising a lens assembly and comfort pad attached to a portable tabletdevice having a camera.

FIG. 16 is a front view of the scleral strain monitoring system of FIG.15 in use.

FIG. 17 is a graph showing the measured relationship betweenperipapillary meridional strain and intraocular pressure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The detailed description set forth below is intended as a description ofthe presently preferred embodiment of the invention, and is not intendedto represent the only form in which the present invention may beconstructed or utilized. The description sets forth the functions andsequences of steps for constructing and operating the invention. It isto be understood, however, that the same or equivalent functions andsequences may be accomplished by different embodiments and that they arealso intended to be encompassed within the scope of the invention.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained. It is noted that, as used inthis specification and the appended claims, the singular forms “a,”“an,” and “the,” include plural references unless expressly andunequivocally limited to one referent. As used herein, the term“include” and its grammatical variants are intended to be non-limiting,such that recitation of items in a list is not to the exclusion of otherlike items that can be substituted or added to the listed items. As usedherein, the term “comprising” means including elements or steps that areidentified following that term, but any such elements or steps are notexhaustive, and an embodiment can include other elements or steps.

Sensor Based System for Monitoring Eye Health:

A system for monitoring eye health comprising: a scleral strain monitoradapted to be implanted in an eye, the scleral strain monitor comprising

-   -   a) a sensor configured to measure electrical resistance between        two electrical conductors, and to generate a signal representing        said electrical resistance;    -   b) a transmitter configured to transmit the signal; and    -   c) a reader adapted to be located outside the eye, the reader        being configured to receive information transmitted by the        transmitter.

A method of monitoring eye health comprising: providing a scleral strainmonitor adapted to be implanted in an eye, the scleral strain monitorcomprising

-   -   a) a sensor configured to measure electrical resistance between        two electrical conductors, and to generate a signal representing        said electrical resistance, the sensor comprising at least first        and second anchor members being spaced apart from one another,        the first and second anchor members being adapted to be secured        to respective first and second anchor locations on or in a        ciliary body;    -   b) a transmitter configured to transmit the signal; and    -   c) a reader adapted to be located outside the eye for receiving        information transmitted by the transmitter.

The features, aspects and advantages of the developments will now bedescribed with reference to the drawings of several embodiments, whichare intended to be within the scope of the invention herein disclosed.These and other embodiments will become readily apparent to thoseskilled in the art from the following detailed description of theembodiments having reference to the attached figures, the invention notbeing limited to any particular embodiment(s) disclosed.

Although the exact etiology of glaucoma remains unknown, it is generallyunderstood that excessively high intraocular pressure (IOP), which maybe caused by a flow obstruction in the trabecular meshwork, causesdamage to the optic nerve and leads to permanent loss of vision.Accordingly, conventional methods for preventing the onset andprogression of glaucoma all involve monitoring patients for high IOP,typically through intermittent measurements performed on an in-patientbasis. More recent approaches propose continuous monitoring of IOP,either through an implantable IOP sensor or a contact lens IOP sensor.Yet it has been observed that even patients with statistically normalIOP measurements can develop glaucoma. Still other patients can showelevated levels of IOP while exhibiting no signs of glaucoma, even overextended observation periods. This may occur as a result of the factthat the biomechanical properties of the tissues involved can varysignificantly from patient to patient, creating different responses tovarying IOPs.

In embodiments, an entirely different parameter than IOP—scleralstrain—is the focus of glaucoma prevention and monitoring efforts. Bymeasuring mechanical strain at the surface of the sclera, instead of (orin addition to) intraocular pressure, embodiments provide a moreaccurate indicator of glaucoma risk which takes into account thebiomechanical characteristics of each patient's ocular tissues.Embodiments provide a strain sensor which is anchored to two or morediscrete points or regions on or in the sclera (or tissues adjacent tothe sclera such as the ciliary body) and which is highly elastic inbetween those points, so as configured to provide an accurate indicationof scleral strain in otherwise unrestricted ocular tissues.

With reference now to FIG. 1A, a front side view of an implant 100forming part of a system for measuring eye health is shown. In theembodiment illustrated in FIG. 1A, the implant 100 includes anintraocular lens (IOL) 102 and a strain sensor 104 connected to the IOL102. In some embodiments, the IOL 102 includes one or more haptics 106.In some embodiments, the implant 100 has a major dimension or length(from the top to the bottom as shown in FIG. 1A) between about 10 and 15mm, or a length less than or greater than either of these numbers. Forexample, in some embodiments, the implant 100 has a length of about 13mm. In some embodiments, the implant 100 has a minor dimension or width(from side to side as shown in FIG. 1A) of between about 5 and 10 mm, ora length less than or greater than either of these numbers. For example,in some embodiments, the implant 100 has a width of about 6 mm.

In some embodiments, the sensor 104 is formed separately from andconnected to one of the haptics 106, while in other embodiments (asillustrated in FIGS. 1A and 1B), all or part of a haptic 106 forms aportion of the sensor 104. In some embodiments, the sensor 104 includesa proximal anchor member 108 and a distal anchor member 110 that arespaced apart from one another along the length of the haptic 106 (oralong the circumference of the eye, as implanted). The anchor members108, 110 are each configured to securely attach to separate areas on orin the sclera (or ciliary body) of the eye when the IOL 102 isimplanted. In some embodiments, the anchor members 108, 110 are spacedapart by a distance of about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15mm, or a distance less than, greater than, or within a range defined byany of these numbers.

In some embodiments, the implant 100 further includes a circuit board112, which includes a data logger and/or microprocessor to store,wirelessly send, and/or process the data measured from the sensor 104,and which, in certain embodiments, is connected to the sensor 104 by anelectrical circuit 114. In some embodiments, the circuitry in 112 isalso used to harvest wireless energy, such as that from an external unitthat sends the implant energy and receives the implant's data. In someembodiments, the implant 100 also includes an antenna coil 116 totransmit and receive data measured from the sensor or processed by amicroprocessor. In certain embodiments, the circuit 114 and the coil 116are disposed so as not to impede vision once the implant 100 isimplanted.

Various configurations of a strain sensor 104 may be used with theimplant 100. The strain sensors 104 comprise different sensorconfigurations and different sensor locations in the variousembodiments. In these embodiments, depending on the anatomy of thepatient, the nature of the disease, and the preference of the healthcarepractitioner, a combination of the sensor configuration and sensorlocation can be used.

FIG. 1B shows a top view of one embodiments of the strain sensor 104 andbetter illustrates the relative locations of the proximal anchor member108 and the distal anchor member 110. The strain sensor 104 includes afirst fixed member 120 (which, in the illustrated embodiment, is formedby a portion of the haptic 106), a second fixed member 122, and amovable member 124, which is disposed between the first and second fixedmembers 120, 122. In some embodiments, the fixed members 120, 122 andthe movable member 124 are rigid. The proximal anchor member 108 isoptionally disposed on, extends from, or forms part of the first fixedmember 120 such that it is optionally secured to a first location on orin the sclera. The distal anchor member 110 is optionally disposed on,extends from, or forms part of the movable member 124 such that it isoptionally secured to a second, spaced-apart location on or in thesclera.

In some embodiments, the fixed members 120, 122 and the movable member124 are encapsulated in or otherwise disposed in a highly elasticmaterial (for example having a Young's Modulus equal to or lower thanthat of the ocular tissue(s) to which the anchor members 108, 110 aresecured) such that the anchor members 108, 110 move freely with respectto one another, at least in the direction indicated by arrow A. Forexample, in some embodiments, the fixed members 120, 122 and the movablemember are encapsulated in silicone having a suitably low Young'sModulus. In some embodiments, the movable member 124 are disposed in afluid, such as silicone gel, Viscoat® fluid available from AlconLaboratories, or a balanced salt solution (BSS), which can be surroundedby an encapsulation material such as silicone. By such a configuration,once the anchor members 108, 110 are secured to the sclera, the distalanchor member 110 (and the movable member 124 to which it is connected)moves away from and/or back toward the proximal anchor member 108 as thesclera expands or contracts and the scleral strain is measured. In someembodiments, the encapsulated fluid serves to back fill in any voidsgenerated by the motion of the member 124 relative to members 120, 122.

In embodiments, the anchor members 108, 110 has any configurationsuitable for anchoring at least two discrete points or regions of thesensor 104 to two discrete points or regions on or in the sclera. Forexample, in some embodiments, the anchor members are rigid spikesconfigured to at least partially penetrate and anchor in ocular tissues.In other embodiments, the anchor members are discrete points or regionsdisposed, respectively, on fixed and movable portions of the sensorwhich are configured to be secured to the ocular tissues withbiocompatible glue such as, for example, fibrin glue. In still otherembodiments, the anchor members are discrete points, regions, oropenings disposed, respectively, on fixed and movable portions of thesensor which are configured to be secured to the ocular tissues withsutures.

FIG. 1C shows a more detailed top view of the embodiment of the strainsensor 104 that was shown in FIG. 1B, and illustrates one possiblearrangement of resistors 130 in the strain sensor 104. As illustrated inFIG. 1C, the first fixed member 120 includes a plurality of resistors130(a), 130(b), 130(c), 130(d), 130(e), 130(f), and 130(g) connected inseries to a plurality of conductors 134(a), 134(b), 134(c), 134(d),134(e), 134(f), 134(g), and 134(h), which can be exposed along a surfaceof the first fixed member 120. Each of the conductors 134 are spacedapart by a distance B. The second fixed member 122 includes a pluralityof resistors 132(a), 132(b), 132(c), 132(d), 132(e), and 132(f), and132(g) connected in series to a plurality of conductors 136(a), 136(b),136(c), 136(d), 136(e), 136(f), and 136(g), and 136(h), which areexposed along a surface of the second fixed member 122. Each of theconductors 136 is also spaced apart by a distance B and disposedopposite each of the conductors 134. Each set of conductors 134 and 136is connected to the circuit 114 via at least one wire 138. The movablemember 124 includes a connecting bar 140 having a width C. Theconnecting bar 140 is exposed at opposing surfaces of the movable member124 such that it is configured to contact a different pair of resistors130, 132 when the movable member 124 is in different lateral positionswith respect to the fixed members 120, 122. In this way, as the scleraexpands or stretches, the connecting bar 140 moves with the movablemember 124 and closes the circuit between a different set of resistors130, 132. For example, when the connecting bar 140 is in a position toconnect conductors 134(c) and 136(c), the circuit 114 measures aresistance including resistors 130(a), 130(b), 132(a), and 132(b). Thus,a different level of resistance measured by the sensor 104 correlates toa different distance between anchor members 108 and 110 and,accordingly, to a different amount of scleral strain. In someembodiments, the width C of the connecting bar 140 is roughly the sameas the distance B between each of the conductors 134, 136. In otherembodiments, the width C of the connecting bar 140 is slightly less thanthe distance B between each of the conductors 134, 136, so as to avoidnoise caused by slight motion of the sensor 104 or of the sclera. Insome embodiments, connecting bar 140 is spring loaded such that it isflexed into a state prior to assembly that causes it to naturally pushagainst conductors 134 and 136, ensuring proper electrical contact.

In this way, embodiments provide accurate measurements regarding scleralstrain without necessarily requiring precise measurements of resistance,because any significant increase or decrease in resistance correlates toa specific change in the distance between (i.e, displacement of) theanchor members 108, 110. Put another way, embodiments provide accurateindications of scleral strain without requiring calibration of thesensor with respect to measurements of resistance. Thus, embodimentsoffer healthcare practitioners and patients confidence in strainreadings even years after implantation.

In some embodiments, either or both of the fixed members 120, 122 areformed from any suitable rigid material, including, for example andwithout limitation, silicon. The resistors 130, 132 and the conductors134, 136 are formed or embedded in the material forming the fixedmembers, with insulating material disposed so as to electrically isolateneighboring conductor/resistor sets from one another. In someembodiments, the movable member 124 is formed from silicon or any othersuitable rigid material. The connecting bar 140 is formed or embedded inthe material forming the movable member.

Although the embodiment illustrated in FIG. 1C includes seven resistorsin each fixed member for purposes of illustration (i.e., seven pairs or“stages” of resistors, with fourteen resistors overall), embodiments caninclude any number and arrangement of resistors suitable for theirintended purpose. For example and without limitation, embodiments caninclude 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260,280, 300, 400, or 500 discrete resistors, or a number of resistors lessthan, greater than, or within a range defined by any of these numbers.The resistors can be arranged in a single row (with each subsequentresistor in the row corresponding to a “stage”), arranged in pairs (witheach pair of resistors corresponding to a “stage”), or arranged in anyother configuration suitable for their intended purpose. For example, insome embodiments, the resistors need not be arranged in a straight lineor even in the same plane; instead, the resistors can be arranged in acurvilinear pattern or in coplanar or non-coplanar arrangements.Further, although the embodiment illustrated in FIG. 1C shows two rowsof resistors 130, 132, some embodiments can include only a single row ofresistors and a single conducting electrode. In such an embodiment,either the row of resistors or the conducting electrode can be movablewith respect to the proximal anchor member, and the distal anchor membercan be disposed on the movable portion.

FIGS. 8A-8B show a detailed side view of the embodiment of a first fixedmember 120 and a movable member 124.

Sclera strain levels indicative of glaucoma risk are expected to be onthe order of about 1%. Accordingly, in some embodiments, the sensor 104is configured to measure and/or record strain values of between about 0and about 2%, 4%, 6%, 8%, 10%, or more, or a strain value less than,greater than, or within a range defined by any of these numbers. In someembodiments, the sensor 104 is configured to measure and record strainvalues of between about 1% and 7%. In some embodiments, the sensor 104is configured to measure and/or record strain in increments of about0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%,0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or 0.8%, or 1%, or inincrements less than, greater than, or within a range defined by any ofthese numbers. For example and without limitation, in one embodiment,the resistors 130, 132 are arranged so that each stage (or, eachincrease or decrease in measured resistance) corresponds to a change inscleral strain of approximately 0.01%.

In some embodiments, the spacing B between each of the conductors 134,136 is any distance suitable for the intended purpose. For example andwithout limitation, the distance B between each of the conductors 134,136 is about 0.001 mm, 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.2 mm, 0.3mm, 0.4 mm, 0.5 mm, or a distance less than, greater than, or within arange defined by any of these numbers. Likewise, the width C of theconnecting bar 140 is any width suitable for its intended purpose. Forexample and without limitation, the width C is about or slightly lessthan 0.001 mm, 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4mm, 0.5 mm, or a width less than, greater than, or within a rangedefined by any of these numbers. For example and without limitation, inone embodiment, a sensor 104 includes two rows of 25 resistors each,with the resistors in each row spaced apart by about 0.4 mm, so as tospan a length of approximately 10 mm.

In some embodiments, each resistor 130, 132 has the same resistance,such that connection of each additional resistor 130, 132 in seriesresults in roughly the same incremental increase in resistance. Forexample, in one embodiment, each resistor 130, 132 has a resistance ofapproximately 100 ohms. In other embodiments, each resistor isconfigured with a different resistance, for example such that connectionof each additional resistor 130, 132 in series results in a more widelyvarying change in resistance. In some embodiments, the resistors in eachset 130, 132 has an increasingly higher (i.e., graduated) level ofresistance so as to reflect a marked difference between each connectinglocation, thereby minimizing the effect of minor fluctuations inresistance, minor movements of the sclera caused by motion of thepatient, or other noise. For example and without limitation, one or bothof the first resistors 130(a), 132(a) can have a resistance of about 10ohms, one or both of the second resistors 130(b), 132(b) can have aresistance of about 100 ohms, one or both of the third resistors 130(c),132(c) can have a resistance of about 1000 ohms, and so forth. In someembodiments, the level of resistance is such that it approximates alevel of displacement of equal value (in different units). For example,the physical separation of each stage might be 10 microns and theincrease in resistance from one stage to the next can be 10 kilo-ohms,requiring no computation for converting resistance changes to physicaldisplacement.

Further, although the embodiment illustrated in FIG. 1C shows each rowof resistors 130, 132 connected in series, some embodiments includeresistors which are connected in parallel instead of in series. In suchan embodiment, each resistor is configured with a different and possiblyunique resistance (which can be increasing, decreasing, or randomlyvaried along the array of resistors) such that a particular resistancemeasurement corresponds to a particular displacement of the fixed andmovable members and a corresponding level of strain.

In some embodiments, the sensor 104 is configured to provide anindication of IOP in addition to scleral strain. For example, someembodiments incorporate a transfer function which relates measuredresistance and/or strain to IOP, based on an initial calibration of theIOP measurement. In some such embodiments, the resistors 130, 132 arearranged so that each stage (or, each increase or decrease in measuredresistance) corresponds to a change in IOP of roughly 0.5 mm Hg. Forexample, in one embodiment, an implant 100 includes 200 discreteresistors arranged in 100 pairs or stages, with each stage spaced apartsuch that the sensor is configured to measure IOPs from about 0 to about50 mm Hg.

The sensor 104 and its components are formed in any suitable fashion.For example, in some embodiments, the sensor 104 is formed using MEMSmanufacturing methods, including, for example and without limitation,depositing layers or areas of conductive material (such as gold) on orin layers or areas of silicon.

FIGS. 2A-2D illustrate examples of various types of resistors that areused in embodiments. For example and without limitation, FIG. 2A shows awire resistor 150 having a zig-zag configuration connected to conductors160. In one embodiment, the wire resistor 150 includes a 1 micron wirein a zig-zag configuration having dimensions of approximately 0.1 mm by0.1 mm. In some embodiments, resistors are formed by wires of differentdiameters or of different lengths. In some embodiments, each wire iscoated with insulating material or otherwise insulated from neighboringwires. FIG. 2B shows an off-the-shelf resistor 152, which can be, forexample, a ROHM 03015 chip resistor (ROHM Co., Ltd. Kyoto, Japan), whichis 0.3 mm by 0.15 mm by 0.10 mm or size 01005 resistors available fromTopline Corporation of Milledgeville, Ga. FIG. 2C shows another wireresistor 154 having a coil configuration connected to conductors 160.FIG. 2D shows still another resistor 156 which is formed from dopedsilicon, and which is connected to conductors 160. For example, in someembodiments, the fixed members 120, 122 is formed from silicon, and theresistors are formed by doping certain portions of the silicon to formresistive elements.

FIGS. 7A-7B illustrate an example of a type of resistor that may be usedin the embodiments herein. In one embodiment, the resistor of FIGS.7A-7B may be arranged in series of 10, 11, 12, 13, 14, 15, 16, 17, 18,19 and 20 resistors in series. In another embodiment, the resistors inseries are 10 kΩ resistors. As an example, as shown in Table 1, theresistors of FIGS. 7A and 7B arranged in series and in resultantresistance testing demonstrated the proper resistance when the sensor ismoved back and forth across the range of the sensors movement.

TABLE 1 Resistor Values Across The Sensor Resistor # 1 2 3 4 5 6 7 8 910 11 12 13 14 15 Value 10 20 30 40 50 60 70 80 90 100 110 120 130 140150 (kΩ)

Alternatively or in addition to resistive elements, some embodimentsinclude capacitive elements to measure strain in terms of capacitance.In embodiments, the resistive (or capacitive) elements are non-resonantor resonant. In embodiments incorporating resonant elements, theresistance (or capacitance) is read by RF-scanning for the resonantfrequency. Further, some embodiments include a sensor comprising acompliant, elastomer-based strain gauge (for example comprising carbonnanotubes) configured to conform to ocular tissues and accuratelymeasure the levels of strain expected therein. One example of such asensor includes thin carbon-black-doped poly(dimethylsiloxane) for thestrain gauge(s) and thick carbon-nanotube-doped PDMS for theinterconnects. In some of these embodiments, the sensor 104 based on thecarbon nanotubes is not configured similar to the sensor shown in FIG.1B. Instead, the sensor 104 in FIG. 1A is a sheet of the carbonnanotube-doped PDMS or similar high yield material that provideselectrical changes as function of mechanical stretch.

With reference now to FIG. 3A, a sensor 200 according to anotherembodiment is illustrated. The sensor 200 includes a fixed member 202and a movable (relative to member 202) member 204. The fixed member 202includes a first anchor member 206 and the movable member 204 includes asecond anchor member 208. The anchor members 206, 208 are configured tobe secured to discrete regions or points on or in the sclera, and to befreely movable with respect to one another as the sclera expands orcontracts (the double arrow of FIG. 3A). In some embodiments, the anchormember 208 includes all or part of a lower surface of the movable member204. An electrode 210 extends from the fixed member 202. The movablemember 204 includes an array of conductors 212(a)-212(f) which areelectrically isolated from one another and from any surroundingcomponents by insulators 214(a)-214(g) and which are connected,respectively, to an array of resistors 216(a)-216(f). As the scleraexpands, the second anchor member 208 moves away from the first anchormember 206 such that the electrode 210 closes the electrical circuitbetween a different set of conductors 212 and resistors 216 andtherefore reflect a different level of resistance. In some embodiments,the sensor 200 and its components are encapsulated in any suitablyelastic material, such as, for example, a silicone having a low Young'smodulus. At a lower level of the sensor 200 (below the plane of thepage, as illustrated in FIG. 3A), the anchor members 206 and 208 arefixed in a highly elastic material. At a middle level of the sensor(within the plane of the page, as illustrated in FIG. 3B), the anchormember 206 is fixed in a highly elastic material, while the electrode210 and/or the movable member 204 is surrounded by a fluid or gel so asto allow free movement of the movable member 204 with respect to theelectrode 210.

As shown in FIG. 3A, the anchor members 206 and 208 move with respect toone another as the sclera expands or contracts. The silicon bar on theleft provide support for the electrode 210. In some embodiments, thesupport is needed because the electrode 210 is flexed prior to assemblyinto the sensor, thus causing it to press against the conductors 212,ensuring a proper electrical contact.

FIG. 3B shows a middle level of the sensor 200, with the resistors216(a)-216(f) removed for clarity. An encapsulation material 218 is alsoshown. FIG. 3B illustrates that, at an IOP of 8 mm Hg, the displacementof the anchor members 206, 208 is L. and the measured resistance willreflect connection of the electrode 210 to conductor 212(d) (and,accordingly, resistor 216(d)). At a higher IOP of 30 mm Hg, thedisplacement of the anchor members 206, 208 is L+2(Δx), and the measuredresistance reflects connection of the electrode 210 to conductor 212(b)(and, accordingly, resistor 216(b)). It should be noted that in thisembodiment, the resistor 210 does not change its shape during themovement. Simply, the resistor 210 moves from a first position to asecond position, thereby causing a difference in the connectivity to aconductor 212.

FIG. 3C shows a sensor 240 according to another embodiment. The sensor240 includes a fixed member 242 and a movable member 244. The fixedmember 242 includes a first anchor member 246 and the movable member 244includes a second anchor member 248. An electrode 250 extends from thefixed member 242. The movable member 244 includes an array of conductors252(a)-252(e), which are electrically isolated from one another and fromany surrounding components by insulators 254(a)-254(f), and which areconnected, respectively, to an array of resistors 256(a)-256(f). In someembodiments, the resistors 256(a)-256(f) are, for example, off-the-shelfsize 01005 resistors available from Topline Corporation, or ROHM 03015chip resistor, which is 0.3 mm by 0.15 mm by 0.10 mm. As the scleraexpands, the second anchor member 248 moves away from the first anchormember 246 such that the electrode 250 closes the electrical circuitbetween a different set of conductors 252 and resistors 256. In someembodiments, the sensor 240 and its components are encapsulated in anysuitably elastic material, such as, for example, a silicone having a lowYoung's modulus. At a lower level of the sensor 240 (below the plane ofthe page, as illustrated in FIG. 3C), the anchor members 246 and 248 arefixed in a highly elastic material. At a middle level of the sensor(within the plane of the page, as illustrated in FIG. 3C), the anchormember 246 is fixed in a highly elastic material, while the electrode250 and/or the movable member 244 is surrounded by a fluid or gel so asto allow free movement of the movable member 244 with respect to theelectrode 250.

FIG. 3D shows a sensor 280 according to yet another embodiment. Thesensor 280 can have a similar configuration to the sensors 200, 240described above, except that the movable member 284 can include a stackof resistors 296(a)-296(d) such as, for example, size 01005 resistorsavailable from Topline Corporation of or ROHM 03015 chip resistor, whichis 0.3 mm by 0.15 mm by 0.10 mm. Thus, in embodiments, the resistors areinternal or external to the movable member. That is, in some embodiment,the resistors form part of the movable member, while in otherembodiments, the resistors are physically separate from (and merelyelectrically connected to) the movable member within the sensor.

Another embodiment includes a conductive wire-in-tube sensorconfiguration, in which the sensor comprises a wire coated in aninsulating, compliant material and having exposed tips. At one end ofthe sensor (i.e., a first anchor member), the outer tube (or otherinsulating layer) is glued, sutured, or otherwise attached to a point onthe sclera. At the other end of the sensor (i.e., a second anchormember), the exposed end of the wire is glued, sutured, or otherwiseattached (e.g. barbed and engaged with the tissue) to a separate pointon the sclera. As the sclera expands or contracts, the wire stretchesand its resistance changes due to the elongated electrical path. In someembodiments, the wire comprises any suitable conductive material suchas, for example, gold. Such an embodiment is configured withoutencapsulation if desired.

In some embodiments, the encapsulated wire makes of a loop of an antennaon the implant. In these embodiments, the change in the electrical pathlength is detectable by the external reader. For example, the externalreader provides an RF signal that creates an electrical current on theimplant antenna that energizes the implant electronics. The implantelectronics then produce an RF signal that varies with the strain on thesensor. This RF signal is then read by the external reader. In someembodiments, the implant electronics providing this utility is atransponder chip such as those commonly used in RFID tagging. In otherembodiments, the implant electronics includes a SAW (Surface AcousticWave) system design.

With reference now to FIG. 4, a simplified block diagram of a system 400for monitoring eye health in accordance with an embodiment is shown. Thesystem 400 includes an implant 402 configured to be implanted in apatient's eye and to measure scleral strain, and an external reader 404which is optionally worn by the patient (e.g., in or on a pair ofglasses) or is optionally held by the patient or a healthcarepractitioner. The implant 402 optionally includes a strain sensor and atelemetry system (including, for example, a transponder and an antenna)for transmitting data (e.g. electrical measurements, strain readings,and/or IOP calculations) to the external reader 404. In someembodiments, however, the antenna is disposed in or on the readerinstead of in or on the implant. Communication and/or powering of thesensor are optionally performed wirelessly between the telemetry systemand the reader. In some embodiments, however, the implant includes abattery so that external powering is not required. In some embodiments,the reader includes storage and a display to record and display the datareceived from the implant 402. In some embodiments, the reader isconfigured to convert a measured level of resistance to a correspondinglevel of scleral strain. In some embodiments, the reader is alsoconfigured to convert a measured level of resistance to a correspondinglevel of IOP, based at least in part on one or more reference levels ofIOP recorded intraoperatively. In some embodiments, the conversion isperformed by a processor in the implant and simply transmitted (asstrain or level of IOP) to the reader.

In some embodiments, the reader is a wireless reader that communicateswith the sensor using RF technology (e.g., throughinterrogation/response or frequency scanning).

In other embodiments, the reader is a camera that uses visual or thermalimaging to read the strain measurements from the sensor. In the case ofthermal imaging, in some embodiments, at least two spike-type membersare inserted into ocular tissue at some relatively close but measurableseparation distance. As the sclera expands due to increased pressure,the two spikes separate. By intentionally selecting a spike materialthat has a thermal emissivity notably different from the nearby oculartissue, the thermal spacing is externally monitored wirelessly usingthermography. In these embodiments, a 2D thermal imaging hardwareinstalled on the external unit (for example, a pair of eyeglass frames)records multiple digital thermographs of the implant location and, usingpost processing techniques such as averaging the images across time, anaccurate measurement of the spikes separate is realized. For improvedsignal, the spike can be kept close to the ocular surface since it isknown that the water in the ocular tissues will tend to absorb theinfrared radiation. In these and other embodiments, the wader isconfigured to communicate (wirelessly if desired) with a mobile device406 such as a laptop or Smartphone.

In one embodiment, a healthcare practitioner injects a dye into theocular tissues to increase the contrast between the anchor members andthe surrounding tissue, allowing the camera to visually detect thedisplacement (or an increase in displacement) between the anchormembers. This is can be done in a manner similar to that explained abovefor thermography.

In embodiments such that the reader is a wireless reader thatcommunicates with the sensor using RF technology, the external readeroptionally provides an RF signal that creates an electrical current onthe implant antenna that energizes the implant electronics. The implantelectronics then produces an RF signal that varies with the strain onthe sensor and is read by the external reader. In some cases, theimplant electronics is a transponder chip, such as those commonly usedin RFID tagging. In other embodiments, the implant electronics includesa SAW (Surface Acoustic Wave) system design.

As described above, in some embodiments, the implant 100 optionallycomprises an intraocular lens (IOL) having a strain sensor 104 disposedon or in the lens or extending from the lens. In other embodiments, theimplant 100 optionally comprises an intraocular lens (IOL), eitherphakic or pseudophakic, having a strain sensor 104 disposed on or in thelens or extending from the lens. In still other embodiments, for exampleas illustrated in FIG. 5, the implant 100 optionally comprises a plate500 configured to be implanted under the conjunctiva, with a strainsensor 502 disposed on or in the plate or extending from the plate. In aplate configuration, a sensor optionally has at least two anchor membersdisposed, respectively, at spaced-apart locations on or in the platesuch that they are secured to respective locations on or in the sclera.The sensor optionally includes a highly elastic material (for examplehaving a Young's Modulus equal to or lower than that of the oculartissue(s) to which the anchor members are secured) such that the anchormembers are freely movable with respect to one another as the sclera (orother ocular tissue to which they are anchored) expands and contracts.In an embodiment incorporating a plate, the plate is optionally formedfrom a material having a low modulus of elasticity such as, for example,a silicone. In some embodiments, the implant includes an Ahmed valve(available from New World Medical Rancho Cucamonga, Calif.), and havinga drainage tube. In such an embodiment, the anchor members am secured tothe sclera, either under a tube that has previously been implanted orduring trabecular surgery. In some embodiments, the attachment area isthe pars plana. Attachment mechanisms can be small spike members, suchas those shown in IOL versions, ophthalmic glue, such as a fibrin glue,or sutures.

In some embodiments, the implants 100 disclosed herein are implanted inother locations in the eye. For example, in an embodiment comprising anIOL or a PIOL, the anchor members are secured to the ciliary body or atthe pars plana from underneath the sclera. During implantation, thesurgeon can direct the haptic on which the sensor is disposed to thecorrect orientation for anchoring of the anchor members.

Once the implant is in place and the anchor members are secured to theocular tissues, the intraocular pressure can be intraoperativelymanipulated to establish one or more baseline or reference values ofscleral strain and, if desired, to calibrate the sensor for IOPmeasurements. For example, IOP can be intraoperatively lowered down to abaseline level (such as, for example, 10 mm Hg), and a baseline level ofscleral strain can be recorded at that pressure based on the electricalresponse (e.g. the measured resistance) of the sensor. The IOP can thenbe increased to higher levels (such as, for example, up to 30 mm Hgspecific increments, such as 2 mmHg or S mmHg), and a reference level ofscleral strain can be recorded at those higher pressures based on theelectrical response (e.g. the measured resistance) of the sensor. Theseparameters are then used post-operatively to estimate IOP based onmeasured levels of resistance and/or strain.

FIG. 6 is a schematic drawing of an apparatus 600 for intraoperativelymanipulating eye pressure, suitable for use with an embodiment. In someembodiments, the baseline pressure (e.g., 10 mmHg) also serves as aconsistent baseline for the strain measurement, thus providingpatient-to-patient comparisons. For example, one can record a patient'sstrain as “+1%”, which implies 1% increase from the 10 mmHg baseline. Inother words, the notation “+1%” indicates the pressure rise in the eyehas caused the two anchors of the sensor to move a distance of 1% apartfrom that recorded when the patient's pressure was 10 mmHg duringsurgery (e.g., 10.0 mm @ 10 mmHg became 10.1 mm at, say, 15 mmHg).

In another aspect, disclosed herein are methods of monitoring eye healthin a patient using the implant 100. The method comprises the steps ofobtaining an output of electrical resistance from an implanted device inthe eye of an individual, as described herein, comparing the resistanceoutput to a baseline value, and correlating the change in the electricalresistance to a disease state in the individual.

In some embodiments, the baseline value is obtained immediately afterthe device is implanted. In other embodiments, the baseline value isobtained several days after the implantation, to allow for any potentialinflammation of the sclera and other tissue to be resolved. In someembodiments, the change in electrical greater than a certain value, forexample 1, 10, 30, 50, 100, etc., ohms indicates the onset of glaucoma.In other embodiments, the change in electrical resistance is expressedin terms of the distance between the anchor members, as discussed above.In other embodiments, the change in electrical resistance is expressedin terms of a percent increase in the sclera strain, as discussed above.

Sensor Based System for Monitoring Structural Fatigue:

While the embodiments shown in FIGS. 1B, 1C, 2A-2D, and 3A-3D have beenpreviously shown to be used within surgically implanted devices tomonitor scleral strain in an eye, the same concepts can be utilized inother applications, such as attaching to a user's skin for biomechanicalmonitoring. Additionally, the same concepts can be utilized in alarger-scale fashion to monitor strain on any item capable of undergoingstress-related deformation, e.g., buildings, bridges, and otherstructures.

In this larger-scale embodiment, there is envisioned a system formonitoring strain on a structural surface to which the system isattached having at least first and second anchor spaced-apart members.The first and second anchor members are configured to be secured torespective first and second anchor locations on or in the surface to bemonitored. Further, the first and second anchor members are movable withrespect to one another.

The system further includes a sensor having a plurality of resistiveelements. The sensor is configured to measure electrical resistancebetween two electrical conductors and to generate a signal representingsaid electrical resistance. The sensor measures structural strain basedat least in part on a displacement between the first and second anchormembers.

The system further includes a transmitter configured to transmit thesignal and an external reader configured to receive informationtransmitted by the transmitter.

In certain embodiments of this system, the first anchor may be connectedto a resistor housing and the second anchor member may be connected to acomponent housing. Additionally, or alternatively, the sensor mayinclude a plurality of resistive elements, which may be connected inparallel and/or each have a different resistance.

Imaging Based System for Monitoring Eye Health:

In another embodiment, disclosed herein is a system for monitoring eyehealth, the system comprising: a scleral strain monitor comprising

-   -   a) a wearable pair of eyeglasses comprising        -   i. one or more image sensors,        -   ii. a CPU,        -   iii. a memory storage device,        -   iv. one or more connecting wires, and        -   v. and a power source; and    -   b) at least one preselected target region on or in the sclera,

wherein the CPU receives images from the image sensors and thentransmits the images to the memory storage device.

In another embodiment, disclosed herein is a method of monitoring eyehealth, the method comprising: providing a scleral strain monitorcomprising

-   -   a) a wearable pair of eyeglasses comprising        -   i. one or more image sensors,        -   ii. a CPU,        -   iii. a memory storage device,        -   iv. one or more connecting wires,        -   v. and a power source; and    -   b) at least one preselected target region on or in the sclera,

wherein the CPU receives images from the image sensors and thentransmits the images to the memory storage device.

In general, the imaging based systems and methods disclosed specificallypertain to the early detection and diagnosis of glaucoma. The imagingapparatus of the disclosed systems and methods is designed as a wearablepair of eyeglasses capable of viewing the eye and collecting data in theform of images that will aid in the early detection of glaucomasymptoms.

In order to determine scleral strain, it is necessary to sense smalldisplacements of separated points on the sclera. This can be done in anon-contact scenario, through direct imaging of the surface of the eye,if we can either establish image-to-image correspondence of differentpoints on the eye or measure overall characteristics related to scleralsize. We disclose several methods for accomplishing this task, withoutexcluding others that may be obvious extensions or modifications.

-   -   1. Measurement of distance between two symmetric objects        implanted in or placed on the eye.    -   2. Measurement of distance between two asymmetric objects        implanted in or placed on the eye.    -   3. Measurement of distance between two previously characterized        “target regions” on the eye.    -   4. Measurement of the spatial frequency characteristics of one        or more regions of the eye, to establish spatial scale.

Measurement Between Two Symmetric Objects:

Scleral strain is the ratio of the change in a distance to the originalmagnitude of the same distance at rest or at a reference stress level.Given two objects on the sclera, repeated measurements of the distancebetween the objects will give a history of the strain. If one or morereadings can be performed at a known level of strain or intraocularpressure, we can use simple spherical trigonometry to calculate thestrain for any image taken that contains both objects. To increase theaccuracy, we propose the use of geometrically regular objects (such ascircles) for which the centroid can be measured accurately. Accuracy ondetermining object centroids can be much less than one pixel. Refer toFIG. 10 for one possible scenario.

Utilizing a suitable image capture system, images of the sclera of theeye are acquired and processed to determine the positions of two fixedtargets implanted into or placed onto the eye. In some embodiments, thetwo separated symmetric implanted objects are spike-type members andfabricated from surgical steel or Teflon. In some embodiments, the twoseparated symmetric objects may comprise two dots or the two separatedasymmetric objects comprise a dot and an arc. In some embodiments, thetwo separated symmetric objects may comprise markers, the markerscomprising ink or dye. These targets are biologically inert andinelastic, so that the distance between their centroids is an accurateindication of the perimeter of the eye, and thus is proportional to thescleral strain. The image is enhanced and dimensions are extracted. Forthis method, spatial calibration is important and is not delivereddirectly by the method, as the target objects are likely to be too smallto allow their size to indicate spatial resolution sufficientlyaccurately. There are at least two ways to calibrate the images taken:by measuring the radius of the iris or by measuring the displacement ofa light point source impinging on the eye from a known angle to theimaging plane. This “triangulation” method will result in the x-yposition of the point being proportional to the distance from the lightsource to the eye.

Measurement Between Two Asymmetric Objects:

In an actual scenario, it may be that the distance from the imagecollection apparatus to the eye surface varies. Without some correction,this difference in distance could be misinterpreted as a change in thescleral strain. To allow dynamic correction of the working distance, oneof the targets can be designed to give an independent measurement of thespatial calibration (in pixels per millimeter, for example). Referringto FIG. 11, which shows one possible configuration, the large arc objecthas a known radius of curvature that will not change, because of theinelastic nature of the object. In some embodiments, the two separatedasymmetric implanted objects are spike-type members and fabricated fromsurgical steel or Teflon. In some embodiments, the two separatedasymmetric objects may comprise two dots or the two separated asymmetricobjects comprise a dot and an arc. In some embodiments, the twoseparated asymmetric objects may comprise markers, the markerscomprising ink or dye. This can be used to establish the spatialcalibration of the entire scene. Then, measurement of the offset betweenthe two objects can be interpreted as a spatial distance andinsensitivity to change in working distance is achieved.

Measurement Between Two Target Regions:

It may be that the need to implant target objects in the eye isobjectionable or prohibitive in some cases. However, the surface of thesclera has distinct texture due to the patterns of blood vessels andother tissues. By selecting two suitable regions of the sclera someknown distance apart and storing a processed “template” for these areas,standard target locating techniques (such as normalized grayscalecorrelation) can be used to accurately locate the target regions in anyimage of the eye. The measured distance is then an indication of thedifference in strain from the time at which the target templates werestored. We propose storing several target images (three, for example)and measuring the inter-target distances to provide redundant measure ofthe strain. As above, spatial calibration, if desired, can be achievedby either measurement of the radius of the iris, or by a lighttriangulation method. Reliable templates may be collected usinggray-scale enhancements or an edge operator. FIG. 12 shows the conceptof collection of the template images. One method of extracting reliabletargets from a natural image of the eye is shown here; derivingnormalized edge images of areas of the sclera with suitable naturaltexture. In some embodiments, at least one preselected target region aretwo distinct sclera regions. In some embodiments, the two distinctsclera regions are areas of the sclera with distinct textures and with ameasurable distance apart. Within two or more subregions of interest,possibly defined at physiologic calibration time, the edge image isextracted using a standard edge detection method such as difference ofGaussians. These edge images are the templates which will be located insubsequent images using a technique such as normalized gray-scalecorrelation. The relative shift of the located positions is used tocompute the scleral strain.

Measurement of Spatial Frequency Characteristics:

All images with nontrivial content have a spatial frequency “spectrum”,the relation between spatial frequency and ratio of content in theimage. Changes in size of an elastic object in the image result in a“shift” of its spectrum to higher or lower spatial frequencies. Thus, itis possible to find the highest correlation between the trained andsampled frequency spectra, and to interpret the shift as a measure ofthe expansion or contraction of the image. In some embodiments, thepreselected target region is a frequency spectrum of one or more regionsof the eye or the complete surface of the eye. This approach has theadvantage of being global, rather than limited to a certain region ofinterest, and therefore has the potential to be less sensitive to localartifacts or anomalies. As above, spatial calibration can be achieved byeither measurement of the radius of the iris, or by a lighttriangulation method. FIG. 13 shows the spatial frequencies of an imageof an eye.

Targets:

The targets mentioned above may be implanted devices fabricated from abiologically inert material such as surgical steel or Teflon. Thisallows for geometrically precise manufacture. Alternatively, the targetsmay be markers placed onto the surface of the eye, composed of a safeink or dye product. In some embodiments, the markers may be near-IR ink,such as a fluorescent ink. In another embodiment, the markers may be agentle laser mark. This approach provides a less-invasive markingprocess. One possible approach is to use a marking tool designed toeasily create two “dots” with the proper nominal distance between them.Marking could then be done in an in-office procedure, using such a tool.The concept for this tool is shown in FIG. 14. In some embodiments, thedisclosed systems and method comprise using a dual marking tool forapplying the markers to the surface of an eye as two markers that areseparated by a fixed distance predetermined with the dual marking tool.In some embodiments, the targets or markers are imaged by the one ormore cameras from 2 mm, 3 mm, 4 mm, S mm or 6 mm distance from thelimbus or edge of the iris.

Customization:

Due to variations in physiology, it may be advisable to customize thealgorithmic approach to each individual user. This can be imagined as anin-office visit during which a number of image sets are collected. Atrained operator will examine each image set and process them in anumber of ways, selecting the processing steps that will give the mostaccurate performance. Parameters that may be selected in this processinclude: preprocessing and enhancement, regions of interest, targetsizes and geometries.

Metrics:

The first metric to be extracted, scleral strain, is expected to havethe most direct relationship with IOP and the effects of glaucoma.However, several other metrics will be extracted and continuouslytracked. These may include strain in both axial and tangentialdirections, the ratio of change in strain to strain, and geometricproperties of the eye, such as iris diameter and corneal curvature.Studies suggest that the sclera is more rigid with advanced age, so themapping from strain to intraocular pressure may change over time for agiven user, and other metrics may be used to detect onset of glaucoma.In some embodiments, the ratios of ocular pulse amplitude and IOP are anadditional metric of the disclosed image based systems and methods.

Apparatus:

FIG. 9 illustrates an example of a scleral strain monitor comprising awearable pair of eyeglasses 900 comprising one or more image sensorswith micromotors 904, a CPU and a memory storage device 901, connectingwires 902 and a power source 903. To support the image-based strainmeasurement method, we propose a wearable apparatus such as a pair ofglasses.

In some embodiments, the disclosed image based systems and methods maycomprise the use of a camera with the following specifications:

Type: Mini;

High Definition Support: 1080P (Full-HD);

Memory Card Type: Micro-SD/TF;

Sensor Technology: CMOS;

Video Format: AVI;

Resolution: 1920*1080.30 fps/1280*720/640*480;

Lens Specs: 5 Mege pixels CMOS camera;

Video coding: M-JPEG; and

Power Adaptor: SV DC/500 mAH.

The lenses may be plain or prescription as needed. In the frame, a pairof small digital sensors with optical elements is positioned to captureimages of each eye. The sensors may be facing toward the eyes, or theoptical path may be folded. As shown in FIG. 9, the image sensors may bemounted inside the eyes, in the nosepiece of the glasses, or in theframes to the side of the head. For example, in some embodiments shownin FIG. 9A the image sensors are one or more cameras embedded in theframes of the wearable pair of eyeglasses 900, and located near theouter portion of frames on both sides. The cameras are oriented with thelenses facing the sclera and looking at an outer eye sclera using HDvideo capturing at about 30-60 frames per second. In another embodimentshown in FIG. 9B, the one or more cameras are located near the nose ofthe frames and with lenses oriented to image the inner eye sclera.

In some embodiments, the one or more cameras may comprise one or moreMacro lenses in front of the camera to allow for the short focusingdistance between the eye glass frames and the eye being examined. Insome embodiments, a double macro lens may be employed.

In some embodiments, the disclosed system includes a design includingtwo mirrors near the nose of the frames of the eye glasses aligned atabout 45 degrees relative to each other, such that light of sclera isreflected off one mirror to the other and then into a camera in the noseof the eye glass frames. The design affords the advantage of folding thelight path, which allows for a potentially longer light path andallowing for increased lens power.

A digital signal processor or other CPU extracts the relevantmeasurements proportional to strain from each pair of images, and eitherstores the images and data to a Micro-SIM or other memory card, ortransmits it to a host (Smartphone, wearable computer or nearbycomputer) using an RF connection. In some embodiments, the images aretransmitted with wireless streaming from frames to a Smartphone or othernearby device with computing and internet capabilities.

In some embodiments, the disclosed systems and methods utilize awearable pair of eyeglasses calibrated to take measurements of markersin and on the eye to determine if pressure in the eye has increased bymeasuring sclera stretch and storing the images on an onboard Micro-SIMcard. In some embodiments, the disclosed systems and methods utilize awearable pair of eyeglasses that will store significant sclerameasurements on an onboard Micro-SIM card in order to conserve storagespace with non-significant images. In some embodiments, the disclosedsystems and methods utilize a wearable pair of eyeglasses capable oftransferring the data stored on the Micro-SIM card wirelessly (e.g.,Bluetooth) to a computer or other device for viewing purposes.

Testing will determine the ideal interval for image collection andprocessing. It is anticipated that the data collection interval will bedynamic; for example, a rise in pressure might trigger more frequentdata collection. This aperiodic collection of data may be based onprevious data collected and allow for reduced collection of data toextend battery life of the system.

Imaging Spectrum:

It will be advantageous to control the illumination for acquiring theeye images. In some embodiments, the wearable pair of eyeglasses furthercomprises one or more illumination sources capable of controlling theillumination levels of an eye of a wearer. Various illuminationapproaches may be used to provide illumination of the eye underexamination (i.e., Red, Infrared, LED's, etc). In some embodiments, oneor more illumination sources is capable of emitting light at 800 nm.However, it is undesirable to shine a light, either continuous orpulsed, at the eye; this could cause distractions and would certainly beannoying. We propose to use a illumination source that isnon-distracting. One way to do this is to illuminate in thenear-infrared part of the EM spectrum, nominally at 800 nm. Light inthis range is essentially invisible to the human eye, but most CMOSimagers can readily capture light in this range. Other options foreliminating or reducing the annoyance of the illuminator exist and maybe part of relevant systems.

In some embodiments, the software that tracks and categorizes theconjunctiva (darker) veins verses the sclera (fainter) veins either byrelative image intensity or recognizing which veins move relative toother veins as patient moves eye.

Spatial Calibration:

As mentioned above, the measured displacement must be well-calibrated tobe compared to the baseline measurement, for calculation of strain. Thenature of a wearable device such as glasses makes it difficult toguarantee that the optical working distance will remain constant; onesolution is to calculate the spatial resolution in the imaging planefrom the image itself, thereby provide a correlation between pixels andan absolute spatial value, such as millimeters. Among the methods to dothis are: selection of a target that contains precise dimensionalinformation independent of strain, such as a portion of an arc withknown radius; measurement and computation of the radius of the iris; andlight triangulation to measure the working distance itself.

In some embodiments, the system needs only to monitor the change indisplacement relative to initial displacement in an accurate manner andmay not need to provide a conversion from pixels to an absolute spatialvalue, such as millimeters. However, the depth of field may causeartificial signal (i.e, measurement noise) since objects in the back ofthe depth of field appears to grow by about 10% when moving to the frontedge of the depth of field. In some embodiments, the mechanical mountingof the lens in front of the imaging sensor translates such that thedistance between the lens and sensor can be easily controlled via amicrometer in a fashion very similar to autofocus systems common oncurrent camera systems. In another embodiment, the lens begins at oneextreme position, causing images to be out of focus, and then moves suchthat images become in focus and continues to translate until the otherextreme position is obtained and images are again out of focus. In someembodiments, approximately 50-100 images are captured during thisprocess with both early images and late images being out of focus. Eachimage to be used for strain analysis can then be, for example, the firstimage in which the marker (veins) of interest becomes in focus as onemoves frame-by-frame through the video starting with the camera too faraway for the maker to be in focus. These positions are termed“just-in-focus-small” where the “small” distinguishes the images fromthe just-in-focus-large images, which would be observed if the camerawere too close to be in focus and slowly moving further back until themarker was in focus. In the latter, the marker would appearapproximately 10% larger than in the just-in-focus-small images.Similarly, the just-in-focus large images could be used for analysis.

Physiologic Calibration:

The method further comprises establishing a physiologic calibration ofthe seleral strain, the physiologic calibration comprising

-   -   a) tilting a wearer in a reclining chair or a reclining bench        from an upright position to a backwards supline position and a        range of selected angles between the positions;    -   b) collecting an intraocular measurement from the wearer with a        tonometer at each of the selected angles;    -   c) collecting a scleral strain measurement with the reader at        each of the selected angles and converting the scleral strain        measurements to the corresponding calculated interocular        measurements;    -   d) comparing the interocular measurements of Step b) with the        calculated interocular measurements of Step c); and    -   e) adjusting the reader to align the scleral strain measurements        and repeat to confirm that the reader is calibrated against the        interocular measurements of Step b).

In some embodiments, an accelerometer is integrated into the eye glassesand communicates with the on-board CPU. The accelerometer is used bysystem such the software can take into account if IOP (Strain) increasessimply due to body position (when patient is not in physiologicalcalibration) and can also provide an accurate means of measuring theangle of the reclining in step (c) during the wearer's physiologicalcalibration. On board hardware could include temperature and/or pressuresensors as well, to further explain changes in scleral strain, as IOPchanges can be induced by environmental changes such as a lower-pressureairplane cabin.

The method further comprises establishing a physiologic calibration ofthe scleral strain, the physiologic calibration comprising administeringglaucoma medication at a does suitable for lowering an intraocularpressure of the eye.

Use as a reliable glaucoma monitoring tool requires that the wearableapparatus and software be calibrated to the wearer. This may be done aspart of an in-office visit. In one possible approach, the wearableapparatus is used to conduct measurements from the eyes, while astandard intraocular pressure measurement system is used. Thecombination of these two readings establishes the correspondence. Thisprocess is repeated while the wearer is in the normal posture, and whilethey are tilted backwards over a range of angles. Because this tiltingwill naturally increase the IOP, the resulting data produces a graph ofthe measured transfer function, allowing subsequent mapping back from ameasured scleral strain to an intraocular pressure. In the disclosedmethods, the recliner may be a reclining chair (i.e., ophthalmicexamination chair) or a reclining bench.

Tablet Based Imaging System for Monitoring Eye Health

The imaging based system for monitoring eye health described above isenvisioned to be utilized in an ongoing system wherein the patient wearsthe glasses containing the system the majority of the time.Additionally, or alternatively, similar noncontact imaging concepts maybe utilized on a more infrequent basis performed by a healthcareprovider.

One embodiment envisions the use of a noncontact measurement of scleralstrain that is capable of providing both accurate and convenientreadings using well-vetted algorithms to extract appropriate spatialfeatures with minimal equipment requirements. This can be achieved in aclinic setting via a system 1000 featuring portable tablet computingdevice 1002 containing a camera 1004, with additional optical elements1006 (including, for example, a macro lens and a light source) to givethe proper field of view with a very short working distance as shown inFIGS. 15 and 16. In this embodiment, targeted for use by ophthalmologistand optometrists, a patient's eye 1008 is imaged, (in one embodiment,the blood vessels in the sclera/conjunctiva directly adjacent to thelimbus) while the patient's eye pressure is varied to two or more IOPlevels. This can be achieved by changing the body position (standing up,sitting, laying down face up, laying down face down, etc), consumingcaffeine or similar drug, using glaucoma medications known to reduceIOP, short exercise, or other means. From this in-office visit,clinician uses the novel system 1000 to document the patient's frontalscleral strain as a function of IOP, where the latter is measured usingconventional means such as a Goldmann Applanation Tonometer. As IOP isincreased, displacement of the natural features can be calculated fromthe tablet's imagery (e.g., a CMOS-based sensor or the like), creating anew metric—frontal scleral strain—that will track with IOP. In addition,for a given patient, how the relationship between scleral strain and IOPchanges over time presents a third metric—ocular stiffness. The graph ofFIG. 17 shows that ocular stiffness is statically different (stiffer)for patients suffering from Glaucoma.

To meet the need for consistent image resolution (so that image-to-imagedisplacements can be calculated), a sequence of images is acquired whilethe working distance is slightly varied; the optimal focus point can beidentified as representing the nominal lens-to-eye distance, with theknown spatial resolution. One way of varying this is using an inflatablecomfort pad 1010 wherein the pressure inside the pad is varied in asmooth fashion, such as sinusoidally with time. In another embodiment,the distance is varied by a cam residing inside the comfort pad 1010that is connected to an electric motor. A disposable paper layer mayplaced on the pad 1010 and replaced with each use for patient comfortand cleanliness.

Any single image of the eye 1008 will result in a single displacementmeasurement, between a set of natural “fiducial” points on the eye.These fiducials are naturally occurring areas of visual pattern (such asblood vessels) that will be automatically extracted at an initialconsultation (or with manual assistance).

The time-series of displacements over a short period of time is analyzedstatistically to produce reliable and stable metrics. These are comparedto displacements measured at the time of a known IOP reading tocalculate the strain in the sclera. Customization can allow for theapparatus to be used at the correct angle each time, after a short“fitting session”. The methods for utilizing the images and othercalculations are substantially similar to those discussed above inrelation to the wearable imaging system. Furthermore, a tablet screen1012 allows for easy visualization of the patient's eye 1008 by thehealthcare provider while utilizing the system 1000. In additionalembodiments, the tablet screen 1012 may include overlay features or asplit screen to aid the user in aligning the current (live) video imagewith previously captured videos, such as those from other pressurelevels.

Although the foregoing has been described in detail by way ofillustrations and examples for purposes of clarity and understanding, itis apparent to those skilled in the art that certain changes andmodifications may be practiced. Therefore, the description and examplesshould not be construed as limiting the scope of the invention to thespecific embodiments and examples described herein, but rather to alsocover all modification and alternatives coming with the true scope andspirit of the invention. Moreover, not all of the features, aspects andadvantages described herein above are necessarily required to practicethe present invention.

What is claimed is:
 1. A method of monitoring eye health, the methodcomprising measuring scleral strain of a patient by: a) providing ameasurement system comprising: i) a portable tablet computing devicehaving a camera and optical elements attached to the camera; ii) anadjustable comfort pad abutting the tablet and surrounding the opticalelements; b) positioning the measurement system adjacent to an eye ofthe patient so that the camera is positioned in line with the eye; c)determining a first intraocular pressure of the eye; d) capturing atleast one first image of the eye at the first intraocular pressure; e)varying the intraocular pressure of the eye being monitored; f)determining a second intraocular pressure of the eye; and g) capturingat least one second image of the eye at the second intraocular pressure.2. The method of claim 1, wherein the optical elements include a Macrolens and/or a light source.
 3. The method of claim 1, wherein theadjustable comfort pad comprises an inflatable pad configured to inflateand deflate to vary the distance between the tablet and the patient'seye.
 4. The method of claim 1, wherein the adjustable comfort padincludes a movable cam contained within to vary the distance between thetablet and the patient's eye.
 5. The method of claim 1 furthercomprising varying the distance between the camera and the patient's eyewhile capturing the images.
 6. The method of claim 5, wherein sharpnessof focus is used to select the images to be captured for processing. 7.The method of claim 6, wherein the sharpness of focus is used todetermine a working distance between the measurement system and the eyeof the patient.
 8. The method of claim 1, further comprising providing atonometer to collect the intraocular pressure measurement.
 9. The methodof claim 8, wherein the tonometer is a Goldmann applanation tonometer.10. The method of claim 1, wherein the intraocular pressure is varied byat least one method selected from the group consisting of: changing thepatient's body position, providing caffeine to the patient, providingglaucoma medication to the patient, and having the patient performexercise.
 11. The method of claim 1 further comprising the step h)comparing the at least one first image and the at least one second imageto measure a level of scleral strain between the first intraocularpressure and the second intraocular pressure.
 12. The method of claim 1,wherein the portable tablet computing device further includes a screenfor viewing the images.
 13. The method of claim 12, further comprising astep of providing an overlay or split screen view of a live video imageand a previously captured image.
 14. A measurement system for monitoringeye health comprising: a) a portable tablet computing device having acamera; b) optical elements attached to the camera; and c) an adjustablecomfort pad abutting the tablet and surrounding the optical elements.15. The system of claim 14, wherein the optical elements include a Macrolens and/or a light source.
 16. The system of claim 14, wherein theadjustable comfort pad comprises an inflatable pad capable of beinginflated and deflated.
 17. The system of claim 14, wherein theadjustable comfort pad surrounds a movable cam.
 18. The system of claim14, wherein the portable table computing device further includes ascreen capable of displaying images produced by the camera.